Cannot paste images from Qt...?

[WhyNotHugo]

• I have searched open and closed issues for duplicates

Bug Description

I'm using shotman, which uses Qt's clipboard.setImage to copy an image into the clipboard. (Note: I am the developer of this tool, so can debug into it quite deeply).

I've been able to paste from shotman into Firefox, Telegram and other applications.
I've been able to paste from Firefox, Telegram and other applications into Signal.

However, pasting in Signal does nothing. I've tried copying from other sources, and it seems that. I can't quite find a pattern. It seems that only this pair of applications fail.

Steps to Reproduce

1. Take a screenshot using shotman.
2. Paste the screenshot into Signal (press ctrl+v)

Actual Result

Nothing.

Expected Result

Image should be pasted.

Platform Info

Signal Version: v1.39.2
Operating System: ArchLinux

Link to Debug Log

I don't see anything showing up in the logs:

INFO  2020-12-17T10:47:40.694Z Sending a keepalive message
INFO  2020-12-17T10:48:35.803Z Sending a keepalive message
INFO  2020-12-17T10:49:30.900Z Sending a keepalive message
INFO  2020-12-17T10:49:44.130Z Removing notification
INFO  2020-12-17T10:49:45.152Z SQL channel job 1954 (updateConversations) succeeded in 15ms
INFO  2020-12-17T10:49:49.131Z Removing notification
INFO  2020-12-17T10:49:50.157Z SQL channel job 1957 (updateConversations) succeeded in 23ms
INFO  2020-12-17T10:49:54.131Z Removing notification
INFO  2020-12-17T10:49:55.155Z SQL channel job 1960 (updateConversations) succeeded in 17ms
INFO  2020-12-17T10:50:12.240Z Removing notification
INFO  2020-12-17T10:50:17.240Z Removing notification
INFO  2020-12-17T10:50:18.264Z SQL channel job 1963 (updateConversations) succeeded in 20ms
INFO  2020-12-17T10:50:23.320Z SQL channel job 1966 (updateConversations) succeeded in 21ms
INFO  2020-12-17T10:50:25.996Z Sending a keepalive message
INFO  2020-12-17T10:50:27.241Z Removing notification
INFO  2020-12-17T10:50:28.268Z SQL channel job 1970 (updateConversations) succeeded in 17ms
INFO  2020-12-17T10:50:32.241Z Removing notification
INFO  2020-12-17T10:50:33.266Z SQL channel job 1973 (updateConversations) succeeded in 19ms
INFO  2020-12-17T10:50:34.833Z SQL channel job 1976 (updateConversations) succeeded in 14ms
INFO  2020-12-17T10:50:37.241Z Removing notification
INFO  2020-12-17T10:50:42.241Z Removing notification
INFO  2020-12-17T10:50:43.266Z SQL channel job 1979 (updateConversations) succeeded in 21ms
INFO  2020-12-17T10:50:45.869Z Loaded this list of log files from logPath: log.log, log.log.0, log.log.1, log.log.2

[EvanHahn-Signal]

Are there any other Chromium-based apps you're able to paste into (either Chrome itself or another Electron app)? That would help us debug whether this is an issue with Electron/Chromium or our code.

[WhyNotHugo]

The only other Chromium-based app that I have is chromium itself (nightly).

Pasting into https://imgur.com/upload does not work either, so this seems to be a chromium issue? Pasting the same content into firefox works fine.

[EvanHahn-Signal]

That seems like the likely culprit. I've seen a few people online complain about clipboard issues going from Chromium to Qt, but not the other way around. That suggests some sort of incompatibility, though I can't say what because I know very little about Qt and clipboards on Linux. Have you tried this with other Qt apps? Have you tried it on other operating systems? Are you able to copy from Signal/Chromium into Qt?

[WhyNotHugo]

Have you tried this with other Qt apps?

• I can paste from shotman into other Qt apps (tried pasting into telegram-desktop).
• I cannot paste from other Qt apps into Signal (tried copying from telegram-desktop into signal).

Have you tried it on other operating systems?

My non-Linux devices run iOS, so I can't try there.

Are you able to copy from Signal/Chromium into Qt?

It doesn't seem to be possible to copy an image from Signal (there's just no UI for it), so can't test Signal->Qt.

---

It would seem that copy-pasting across GTK and Qt apps works fine interchanging them freely, but chromium-based apps cannot paste images copied from Qt. I can't thing of any GTK app where I can copy an image to try pasting that into signal.

An important side note: I'm exclusively trying copying image blobs. That is, copy data into the clipboard, as an image editor would do. This is very different to what a browser does, where the URL of the image is copied.